Reversible metal-centered reduction empowers a Ni-Corrin to mimic F430.

This communication presents a novel truncated Ni ^II -containing metbalamin and describes its reversible one electron reduction to a catalytically active Ni ^I species, that features cofactor F430 model character. Our results strikingly demonstrate that stabilization of Ni ^I is not restricted to the related hydroporhyrinoid ligands and is of relevance to the application of metallocorrins in (biomimetic) catalysis.